Propeller



Aug. 25, 1942. M, R MULLEN 2,293,912

' PROPELLER A Filed Sept. 9, 1941 W1 TNESSS.- INVENTOR.-

ATTORNEYS.

Milian Emmen,

- while other portions are movable with the hub Patented Aug. 25, 1942 UNITED STATES PATENT OFFICE" 8 Claims. (CL Nil- 163) This invention relates to propellers and, more particularly to the type employed on aircraft, the pitch whereof is controlled in accordance with conditions of flight,

Specifically, the present invention has reference to a controllable pitch propeller assembly of the species disclosed in U. S. A. Patent NO 2,228,776, granted to the present applicant under date of January 14, 1941; and the primary aim now had in view is certain improvements in the patented disclosure effective to include' with the constant speed negative pitch, the minimum positive pitch land 4the minimum negative pitch,

means whereby the respective advantages of fixed negative pitch and of automatically variable negative pitch may be. combined, so as to have a minimum negative pitch 'of other thanfzero," and an automatically variable pitch beyond that minimum- Another object is the provision of means effec-v tive to lower the propeller speed of operation in negative pitch so as to reduce the inherent disadvantage resultant to driving the air away from the cooling surfaces.

A further object is to enable shifting of the normal zero operating' position to a relatively higher speed position.

The foregoing definitions are indicative, in general terms, of the main aims of this invention, while the detailed advantages of the disclosure herein will be best appreciated after an understanding of the following description considered in conjunction with the accompanying sheet of drawings; while the concluding claims more concisely express the features of novelty over the prior art.

In the drawing:

Fig. 1 is a diagrammatic view showing the electrical circuit connections for controlling an aircraft propeller in accordance with the instant improvements; and, Y Fig. 2 is a fragmentary and part sectional view of a propeller controlled by the means of Fig. l.

Referring more in detail to the drawing which' is substantiallyslmilar to those of Patent No. 2,228,776, hereinbefore referred to, the propeller shaft is designated by the reference numeral 3, while 4 indicates the hub and 5 the blades. 'Ihe blades 5 are arranged, in conformity with known practice, for simultaneous rotation to shift the position of their respective leading edges for changing the pitch 'of the propeller. The control assembly includes a stationary portion mounted on the aeroplaneadjacentthe shaft 3,

a housing 6 secured to 1 is driven by the shaft feathering control and in part located in said hub. A governor 3, while a main switch 8 and a switch 9, also mounted on a xed portion of the aeroplane, are included in the hook-up assembly to powerleacls Ill, Il.

The 'pitch adjusting and controlling motor I2, Fig. 2, has an armature I3 with oppositely wound field coils I4, I5, for rotation of said motor in the desired'drection; and at least one control sleeve I1 loperable 'with the propeller blades 5; while I8, I 8 designate the brush commutators. The shaft I9 voi? the motor I2 is coordinated by 'gears' 20 to a gear- 2|, at the inner ends of each blade 5, and whereby they are all simultaneously moved; while a spring-loaded magnetic brake 22 holds the amature I3 at rest, when the field coils I4, I5 are de-energlzed. The armature I3 is f ing range While the Strips 30, 3| are served with electric energy, in series with the coils I4, I5, from a power lead I8 by a conductor 23 and branch 24 to one brush I8' of said armature, and from power lead II by a conductor 25 to the other brush I8.

' The control vsleeve I1 includes insulated conducting strips 28, 28, 38 and 3|; while the heavy dot-and-dall line 32 typically indicates the zero position o.' leading edge of the blade 5, with which said sleeve is associated. Particular attention is directed, at this juncture, tothe fact that, in accordance with the instant improvements, the adjoining terminal portions of the conducting strips negatively .of zero, in Fig. 1, with respect to the corresponding ends .of the strips `28, 29, for resultant provision of a negative governor shuntbetween zero and minimum automatic variable pitch, as conventionally indicated by the short heavy dot-and-dash line 33 in said gure;

preferably adjustable, in a circumferential direction, for a purpose hereinafter set forth. The main Acontrol switch 8 is, preferably, of the three-pole double-throw type; that is to say, it includes three 35 and 36;l three intermediate contacts 38, 38 and 48 to which the blades 42, 43 and 44 of said switch are respectively fulcrumed. Theblade 44 has an intermediate pivot 45 Afor a purpose later on explained, while the switch 8 is also provided with three contacts 46, 41 and 48, for

`negative pitch operation.

45 to the iield winding I5by a conductor 5I, for

30, 3Iare displaced to the right-hand,

forward contact elements 34,.

eilecting positive and negative pitch respectively;

whereas said iield windings are connected to-` gether and to the coil 53 ci the magnetic brake 22, by `a lead 23, and a conductor 24 to the armature brush I8', armature I3 andrbrush I8 to the conductor 25. Two spaced variable resistances 54, 55, respectively, each having a plurality of taps 56, 51 are utilized, the former' 54 being connected at the outer end by a lead 58 to the intermediate contact element '39 of the main switch 8; whereas the latter 55 is similarly connected by a lead 58V to the intermediate contact 38, of said switch. A-lead 58 connects the con; tact of the ieathering-switch 9 with the intermediate contact 48 of the main switch 8; while said feathering-switch also includes another contact 82 for ensuring, under certain conditions, a full feather-ing position for the propeller blades l .,5, by way of a lead 82', in accordance with the .patent before mentioned.

The conventional governor 1 includes a mov- I with the switch element 4I; whereas the outer able member 84, which` changes its position in' accordance with the speedfabove orbelow' a sei lected level under control of adjuster means 65 in'known manner; while said governor, for any particular setting, enables placement of a movable contact 56, having a lead51, in connection with the feathering switch contact V8| whereby said movable contact is shitablekinto engagement with one oi the taps 55" or 55 of the resistance 54, or one of the taps 51, 51', 51" or 51* of the resistance 55, in accordance-wi-th the A operation of the governor 1, in an obvious manner.

It is to be here remarked vthat two oi the conducting strips28, 29 mayV each embrace an arc up to approximately eightyfiive or ninety degrees, and extend in opposite directions from the line 32, which indicates the leading edge of kthe propeller blades 5;` 'whereas the proportionally similar strips 3l, 3| are correspondingly directed with respect to the negative line 33, while there is a suitable gap betweenstrips 38, 3| to prevent hunting."' The contact strip 28 has two associated elements 58. 59 for contact therewith,

the former being connected by a lead 18 to` the main switch contact element 35, and the iatter 59 through a lead 1I to the conductor 58. The contact strip 29 has two similar elements 12, 13 for contact therewith under certain condi'- tions, the ionner 12 being electrically connected by a lead 14 to the main switch contact element 35, and the latter 13 through a lead 15 to the conductor 5|. Similarly the conducting strip 38 has elements", 11.for contact therewith under certain conditions, with leads 18, 19 respectively connected to the vmain switch iorward contact 41 and the'conductor 58; while the conducting strip 3| has corresponding elements 88, 8|, also ,for contact therewith under cer' tain conditions, with leads 82, 83, the former 82 connecting to the main switch reverse element 48, and the latter 83 with the conductor 5I.

In order that the aero position of the respective resistances 54, 55 may be varied, use 1s preferabiy'made of the shunt means now to be described, said means preferably comprising an actuator member 31 with operatively coordinated Switch elements Il, II and Il, in turn pivoted t0- contact members 88, 88 and 81, with leads 8l. 89 and 88, said leads being respectively in conductive connection as follows: 88 with aninner tap 5850i thevariable resistance54; 89 with an inner tap 51' of the variable resistance 55; 90

84; `whereas a like lead 95 intervenes the innermost tap 51", oi the resistance 55, and a contact 96 also within the limits of movement permitted the switch element 84, in order to eiect moving the zero" point to higher and lower speed positions, respectively, without varying the values of the resistances 54, 55. It is highly desirable to operate the engine at a lower speed duringreverse or negative pitch because the propellers 5, when so operating, drive the enltrained air away from the normal cooling surfaces of the engine, and it is therefore desirable to limit the engine power output to approximately fty percent o! that allowable for positive operation. The actuator member'31 is, accordingly, uslidably mounted in any appropriate manner, not shown, for reciprocation by means said switch ismoved over to negative" pitch position the actuator 3 1 correspondingly effects engagement oi.' the switch elements 84, 49 with the associated contacts, 93.

The control sleeve I1 is, preferably, provided with a projection 98, while a cut-out mechanism |88 operates for breaking the circuit'upon contact therewith of vthe projection 99, said mechanism being conveniently interposed in the conductor SUeading to the heid winding I4; whereas another cut-out mechanism IIII, interposed in the conductor 5| leading to theiield winding I5, breaks the circuit, upon engagement by the projection 98.

The mode oi' operation of the control means hereinbefore described will be readily appreciated by those conversant with the art, or upon reier ence to the within mentioned prior Patent No. 2,228,176. It is desired. however, to stress the fact that when it is desirable to maintain the Y proper pitch oi the propeller for constant speed operation of the engine driving said propeller, the feather-ing switch 9 is set with the lever arm I 81 in engagement with the contact (il, as shown, and the governor 1 is adjusted for the required speed; whereas the main switch 8 is set with the blades 42, 43 and 44, in engagement with the positive pitch contact elements 34, 35 and 35, or with the negative pitch contact elements 45, 41 and 48; whereupon certain control cir- Lcuits are thereby closed. All of these circuits are completed only during desired periods by the switch 8 and,in some instances, by parts oi the control sleeve I1. For example, when the leading edge of the propeller blade 5 is in'the negative 'quadrant and normal forward operation is desired, current is fed from the switch 8 independent of the governor 1 and dependent only with the center contact 55' while .the outer 75 upon the blade leading edge position 32 so that,

regardless of engine speed, the blade is immediately swung about its axis to the positive quadrant, the circuit for such movement being completed through the contact strip 28, contact members 68, 69, leads 10, 1I, conductor 50, leld winding |4only when the blade leading edge is in the negative quadrant and the switch 8 in forward position. As the leading edge of the blade 5 passes zero and goes into the forward quadrant, contact strip 28 ceases to engage the contact member 68, 69 and the governor shunting circuit, to the forward eld I4, is inter rupted.

Similarly, when the switch 8 is set for reverse quadrant operation, with the blades 42, 43 and 44 respectively coactive with the negative contact elements 46, 41 and 48, the forward eld I4 may receive current only while the leading edge of the blade 5, as indicated by control sleeve i1, is in the negativequadrant and the contact strip 30 is completing a circuit through contact vmembers 16, 11. Thus any circuits that would plied directly to the reverse eld I5. Similarly the leading' edge of the blade'5 is prevented from entering the negative quadrant during vpositive 4quadrant operation, as the circuit between the switch 8 and the field I5 can be completed only when the leading edge is forward. This is accomplished by routing the circuit through contacts dependent upon thel leading edge position and operated in relation thereto; or, the. contact strip 29 completes the reverse field I5 circuit y through contact members .12, 13 only when it and the blade leading edge reach or come forward of line `32 which is shown at the position of positive pitch minimum, or zero pitch. Incidentally the fine line |03, Fig. 1, designates the full feathered pitch, whereas the line 33 typically indicates the minimum limits of the conducting strips 30, 3| beyond the zero or negative pitch minimum; while the similar ne lines |05, |06, respectively designate the` minimum negative constant speed and the maximum negative speed respectively, with the intervening space the negative constant speed` range, the space be tween the line 32 and line |05 being covered by governor shunting circuits, whereas the line |01 designates the maximum positive constant speed.

Should the blade leading edge Abe in the negative quadrant when `the switch 8 is thrown to positive operating position, there can be no current iiow to eld I5, as the contact strip' 29 is not in position to complete the circuit throughv contact members 12, 13. There is, however, a -circuit completed between the power lead I0 and the forward field I4, both through the governor controlled circuit of switch 8, contact element 34, conductor 50, etc., and through the governor shunting circuit of said switch, contact element 36, lead 10, contact member 68, contact strip 28, contact member 69, lead 1I, conductor 50, through circuit interrupter |00, conductor 50, forward eld I4, etc., until the blade leading edge reaches zero, whereupon contact strip 68, 69, nor to thereby complete the governor shunting circuit.

Energy is supplied to the armature I3 of the pitch adjusting and controlling motor I2, in sel v ries with the i'leld .coils I4 and I5, through the branch conductor 23, magnetic brake coil 53,

branch 24, motor armature I3, and the conductor.

.the governor 1, which moves the contact mem.

ber 66 into engagement with one of the taps 51 of the resistance 55, and a circuit is set up by way ofthe power lead I0, conductor |06, -switch arm |01, leadv 61, movable contact 66, resistance 55, lead 59, switch blade 42, conductor 50, eld

I4, armature I3, and .conductor 26 to power leadl II; whereby provision isv made for automatic pitch change in accordance with the load change on the propeller.

In order that the automatically variable negative pitch may be changed, attention is directed to the fact that the terminal points 16, 11 and 80, 8| of the respective conducting strips 30, 3|

are arcually shifted to the right-hand of thevv line 32 in Fig. l, or the desiredminimum automatically variable negative pitch position, as indicated by the line 33 in said figure: the purpose being to combine the advantages of fixed negative pitch' and automatically variable negative pitch. Immediately upon shifting the switch 8 for negative pitch operation, the negative governor shunting circuit through contact strip 3| and reverse field I5 carries the blades 5 to the minimumnegative constant speed pitch. There the pitch will remain until an increased throttle setting causes `a, further increase of negative pitch through resistance 55, etc., conductor 5|, and reverse field I5. A decreased throttle setting then following will decrease the negative pitch through the governor controlled circuit resistance 54, conductor 58, contact 41, lead 1 8, point 16, strip 30, point 11, lead 19, conductor 50, and forward eld I4 until contact strip 30. moves away from contact with the points 16, 11,*thus interrupting the forward pitch movement 'and leaving a negative pitch value of 10, plus or minus; that is to say the leading edge of blades 5 will be 10 negative pitch at line |05.

Now it will be apparent that when the switch 8 is thrown for operation of the propeller in the negative quadrant, or for coaction of the switch blades 42, 43 and 44, with the contact elements 46, 41 and 48, thel actuator 31 will be correpondingly drawn with consequential engagement between the switch elements 49, 84 and the associated contacts 93, 96, respectively. As a result a governor shunt circuit is completed between the tap 51 of the variable resistance 55, lead 89, contact 86, switch element 49, contact 93, lead 92, tothe outermost tap 51* of the variable resistance 55 whereby provision is made for a minimum automatically variable negative pitch,` inasmuch as the governor shunting circuit carries the propeller blades 45 to the minimum automatically variable negative pitch, at line |05. On

no longer is in position to contact the vmembers the other hand thel conducting strip 3U. by its displacement as aforesaid, interrupts, at slightly beyond the automatically variable negative pitch, the governor controlled forwardl operating circuit including the lead 94' from the tap 56".' of the resistance 54, contact 94, switch elements 84, contact 81, and resistance lead 90 to the contact 56", and thereby prevents further forward movement past that point while the switch 8 is setfor negative pitch operation. Furthermore, it is to be borne in mind that by provision of the actuator 3l and operatively coordinated switch elements 49, 4| and 84 with the associated contacts Bti- 93, 9I-85, 81--96 or 94, a definite means is provided for lowering the speed of operation in negative pitch relative to that in positive pitch.' In other words, the effective position of the resistances 54, 55 is variable by the actuator 31, in the event that physical movement Y of said resistances is impracticable.

For any further understanding of the advantages of this invention, reference should be had to the within mentioned prior patent; and while one specic means has been herein disclosed whereby movement of the main switch 8 to positive pitch position shifts or varies the resistances 54, 55 so as to have the effect of changing the minimum negativeautomatically. variable pitch position to a higher speed position, it is to be understood the same is capable of other forms of embodiment without departing from the spirit of the invention, and the scope of the following claims. Y' Having thus described my invention, I claim: 1. In a controllable pitch propeller assembly of the type described, the combination of a governor of adjustable setting respective to the speed of the propeller; a motor; a contact connected to a source of electrical energy movable by the governor; two spaced variable resistances adjacent said governor, one of which is connected with said contact on` movement of the governor from its neutral position; switch means operable at the will of the operator to determine whether the pitch change is to be to, and in, the negative or positive pitch range; a control means including circuit making and breaking means movable by the propeller blades during change of pitch which shunt the governorv actuated .contact for effecting movement of said blades into the proper range of pitch as determined by the position of the oper- 'ator controlled switch means aforesaid; an auxiliary switch. coordinated to the operator controlled switch means; and electrical means under control of the resistance shifting switches effective, on movement of the operator controlled switch meansto negative'pitch position, to change the constant speed operation beyond minimum negative pitch.

2. 'I'he combination of claim 1, wherein certain of the circuit making and breaking means, operable with the propeller blades, are circumferentially p re-set relative to the leading edge of the respective propeller blades to provide a range independen't of .the governor,and the associated terminal contact members are in electrical connection with the forward and reverse contact elements vof the operator controlled switch means.

3. The combination of claim 1, wherein one of the controlsleeve circuit making and breaking means is in .the form of4 spaced arcual conductive with means opera most taps of the spaced variable resistances to eilect shifting of the normal zero position to a lowerspeed position. .f

5. In a controllable pitch propeller assembly, of the type described, the combination of means for effecting variations in the pitch of the propeller blades; a pitch changing motor for said propeller: at least one governor controlled power circuit for effecting forward adjustment ofthe pitch; at least one power circuit independent of the governor for eiecting reverse adjustment of the pitch; means operable with the propeller blades for interrupting certain of said circuits at a pitch angle negatively `oi zero pitch; other means operable with the propeller blades to interrupt certain'of said circuits at approximately said' zero pitch; and manually operable control means for selectively changing the respective aforementioned circuits to eifect positive or nega-y tive pitch operation.

6. In a controllable pitch propeller assembly of the type described, the combination of means for eilecting variations in the pitch of the propeller blades; a pitch changing motor for` said propeller; a governor controlled power circuit for eiecting forward adjustment of the pitch; a similarly controlled power circuit for eilecting reverse adjustment ofthe pitch; means operable with the propeller blades to interrupt said circuits at the predetermined minimum of the negative automatically variable pitch range; other means operable with an independently controlled power circuit for eiecting reverse adjustment of the pitch; means operable with the blades to interrupt the last mentioned circuit at approximately the vpredetermined minimum ofy the negativeautomatically variable pitch range; and manually operable control means for selectively utilizing certain of the aforesaid circuits and control means to eil'ect forward adjustments of pitch to full-feathering position.

7. In a controllable pitch propeller, the combination `of a hub: blades mounted on said hub tive to variably adjust the pitch thereof; a governor with means for adjusting its setting; power circuits andv control means for eiecting automatic positive pitch variations relative to an approximate zero pontion: means for .eii'ecting changes negatively from any point of such pitch range: selective power circuits with associated control means operative to eifect negative automatically variable pitch with a minimum of other than the zero pomtion aforesaid; and means' independent of the governor, when the leading edge oi' ther propeller blades is in the negative quadrant, to effect normal forward operation of said propeller.

8. Ina controllable pitch propeller, the combination of a hub; blades mounted on said hub with means operative to variably adjust the pitch thereof; a governor with means for adjusting its setting in accordance with the position of a manually operable control means; a power circuit and control means independent ofthe governor to eil'ect full feathering position of the blades;

manually operable means and means operable with the blades combining to effect positive automatically-variable pitch operation in which there is a circuit and means to eiect forward pitch change. with increase in the speed of the governor aforesaid; a circuit with means to eiect forward pitch change independently of the governor While in negative pitch; a circuit and means to effect reverse pitch movement with decrease in governor speed while in positive pitch; manually operable means I and means operable with the blades combining. to effect negative automatically variable pitch operation with a minimum negative pitch of other than and negatively of zero;

said last mentioned manually operable means including a circuit to eiect reverse pitch movement independently of the governor, to the above mentioned minimum negative pitch from points forward thereof, a circuit to effect further reverse pitch movement upon increase in the `governor speed, and another circuit to effect forward movement to said minimum negative pitch upon decrease in the governor speed.

MILTON R. MULLEN. 

